1. Field of the Invention
The present invention relates to an objective lens drive included in an optical pickup capable of recording an information signal on an optical disc and reproducing an information signal recorded on the optical disc, relates to an optical pickup including the objective lens drive, and further relates to an optical disc apparatus including the optical pickup.
2. Description of the Related Art
Various types of optical discs have been used as recording media for recording an information signal thereon. Examples of such optical discs include a compact disc (CD), a digital versatile disc (DVD), and a high-density recording optical disc on which high-density recording and reproduction of a signal is performed using a blue-violet semiconductor laser or the like capable of emitting a light beam having a wavelength of about 405 nm. Also, an optical pickup has been used to record an information signal on or reproduce a recorded information signal from these types of optical discs.
There have been demands for an optical pickup that can provide compatibility with these various types of optical discs. To provide compatibility with optical discs which involve the use of light beams of different wavelengths or have protective layers of different thicknesses, there is provided an optical pickup having a plurality of objective lenses.
An optical pickup having a plurality of objective lenses includes an objective lens drive which includes both a fixed part and a movable part. The movable part of the objective lens drive includes, for example, two objective lenses arranged side by side in a tangential direction or radial direction. The optical pickup uses a different objective lens depending on the format and type of the optical disc.
For such an objective lens drive having two objective lenses in its movable part and an optical pickup having the objective lens drive, it is desirable that the optical axes of the objective lenses be adjusted to be in an optimal state with respect to the optical disc.
For example, Japanese Unexamined Patent Application Publication No. 10-11765 describes a technique in which a spherical washer or the like is provided for skew adjustment which makes the optical axis of a second objective lens parallel with respect to a first objective lens. After the optical axis of the second objective lens is made parallel to that of the first objective lens by using a spherical washer or the like, a movable part is adjusted, when it is attached to a fixed part, such that the optical axis of the first objective lens is made orthogonal to the plane of the optical disc. Thus, the optical axes of the respective objective lenses are adjusted to be, for example, perpendicular to the plane of the optical disc.
However, an adjusting means, such as the spherical washer, for adjusting the optical axis of one objective lens in two axial directions is complex in configuration. Moreover, providing such an adjusting means increases the number of components and weight, and makes it necessary to go through complicated processes since fine adjustment needs to be repeated.